The State of Finnish Coastal Waters in the 1990S
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472 The Finnish Environment The Finnish Environment 472 The state of Finnish coastal waters in the 1990s ENVIRONMENTAL ENVIRONMENTAL PROTECTION PROTECTION The state of Finnish coastal waters in the 1990s Pirkko Kauppila and Saara Bäck (eds) The ecological status of coastal waters still is an important environmental issue. Especially the shallow Finnish coastal zone is in many respects sensitive to pollution and eutrophication. The The state long term point-source loading of watercourses, especially by nutrients and harmful substances, as well as the indirect effects of increasing demand for different land use e.g agriculture and of Finnish coastal waters building activities in catchment areas have had deteriorating effects in many ways. in the 1990s This report is the second national effort to compile monitoring information on the changes in water quality in Finnish coastal waters. The report is based on the results of different monitoring programmes, loading statistics and studies concerning the state of Finnish coastal water areas. In this report data and information have been collected using the national data bases in which the monitoring data are stored and maintained. In addition to nutrients and harmful substances, monitoring data of phytoplankton and macrozoobenthos are also evaluated. Moreover, the available data on phytobenthos changes originated from separate research projects were evaluated. The report covers the years from the the early 1980s to 1998/2000. The report cover the following topics • loading of nutrients and harmful substances originating from different sources • assessment of the effects of loading on chemical and biological water quality in coastal areas • assessment of changes in the state of coastal waters during the 1990s and reasons for those • phytobenthos and macrozoobenthos changes as a measure of the state of coastal waters • changes in fish populations and fisheries ISBN 952-11-0878-9 ISSN 1238-7312 •••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••• FINNISH ENVIRONMENT INSTITUTE P.O.BOX 140, FIN-00251 HELSINKI FINNISH ENVIRONMENT INSTITUTE The publication is also available in the internet http://www.vyh.fi/palvelut/julkaisu/elektro/fe472/fe472.htm ISBN 952-11-0878-9 ISSN 1238-7312 Maps: Maanmittauslaitos, permission no 7/MYY/01 Cover photo: Pirkko Kauppila Page-layout: DTPage Oy Printinghouse: Vammalan Kirjapaino Oy, 2001 ○○○○○○○○○○○○○○○○○○○○○○○○○○○○○○○○○○○ 2 ○○○○○○○○○○ The Finnish Environment 472 Preface The status of Finnish coastal waters is an important environmental issue. Espe- cially the shallow coastal zone is in many respects sensitive to pollution and eutrophication. The long term loading of nutrients and harmful substances of the catchment areas have had deteriorating effects in many ways. Finally the loading reaches coastal waters and affects the coastal zone. Water protection measures based on sound assessment information are urgently needed. Improve- ment of the ecological status of coastal waters and conservation of coastal areas are also required by the EU Water Policy Directive and the Habitats directive as well as by many international agreements, such as the HELCOM convention, the Ramsar convention and the Convention on biodiversity. Numerous scientific articles and areal reports deal with Finnish coastal waters. However, only some reports provide the reader with general view of coastal water quality such as HELCOM periodic assessments of the state of the marine environment of the Baltic Sea. This report is the second national effort to compile information on the changes in water quality in Finnish coastal waters. In addition to nutrients and harmful substances, monitoring data of phytoplankton and macrozoobenthos are also evaluated. Moreover, the available data on phytobenthos changes originated from separate research projects and it was evaluated. The report covers the years from the the early 1980s to the late 1990s. In addition to international, national and administrative requirements, the report also focus on providing information on coastal water state for the public. The assessment is mainly based on the coastal monitoring data produced by the Finnish Environment Institute (FEI). The physical and chemical monitor- ing data in open sea areas originated from the Finnish Institute of Marine Re- search (FIRM). The section on fish catches was delivered by the Finnish Game and Fisheries Research Institute. Numerous scientific arcticles and reports were evaluated to assess the changes in phytobenthos because monitoring data for phytobenthos was not available. Additionally, local pollution control studies were utilized in order to obtain additional information on zoobenthos and harmful substances in polluted water areas. The editors are grateful to the group of the collegues both in FEI and FIRM for their contributions to the report. We would like to express our warmest thanks to Sirkka Vuoristo who finialised the figures of this report, Petri Porvari for his participation to GIS-work, Antti-Räike and Anna-Maija Beloff who participated in compiling the data, Kati Manni, Petri Ekholm, Jussi Vuorenmaa and Jouni Lehtoranta for their contributions to the text for “information boxes”. The Eng- lish language was revised by Michael Bailey. We thank Doc. Matti Perttilä in FIRM and Teija Kirkkala in the Southwest Finland Environment Centre for their valuable comments on the manuscript. ○○○○○○○○○○○○○○○○○○○○○○○○○○○○○○○○ The Finnish Environment 472 ○○○○○○○○○○○○○ 3 ○○○○○○○○○○○○○○○○○○○○○○○○○○○○○○○○○○○ 4 ○○○○○○○○○○ The Finnish Environment 472 Contents Preface .............................................................................................3 1 Introduction .............................................................................7 1.1 Content and purpose of this report ............................................................... 7 1.2 Coastal water monitoring................................................................................ 8 1.3 International framework ............................................................................... 12 2 Main characteristics of Finnish coastal waters......................13 3 Loading of pollutants .............................................................15 3.1 Nutrient loading and its source apportionment ...................................... 15 3.2 Trends in the nutrient loads in 1985–1998 ................................................. 22 3.3 Loading of organic matter and its trends in 1985–1997........................... 27 3.4 Loading of harmful substances ................................................................... 27 4 Hydrography and oxygen conditions......................................30 4.1 Salinity .............................................................................................................. 30 4.2 Oxygen .............................................................................................................. 35 5 Nutrients ................................................................................37 5.1 Spatial distribution of phosphorus and nitrogen .................................... 37 5.1.1 Winter ...................................................................................................... 37 5.1.2 Late summer ........................................................................................... 45 5.1.3 Inorganic N:P ratio ................................................................................ 49 5.2 Trends since the late 1980s ............................................................................ 51 5.2.1 The Gulf of Finland ............................................................................... 51 5.2.2 The Archipelago Sea .............................................................................. 51 5.2.3 The Bothnian Sea and the Bothnian Bay ............................................ 58 6 Changes in phytoplankton .....................................................61 6.1 Areal distribution of phytoplankton chlorophyll a ................................ 61 6.2 Seasonal variations of phytoplankton ....................................................... 64 6.3 Long term changes in phytoplankton ........................................................ 66 6.4 Nuisance algal blooms .................................................................................. 68 7 Changes in phytobenthos .......................................................71 7.1 Species composition of macroalgae ............................................................ 71 7.2 Fucus vesiculosus recovery ............................................................................ 72 7.3 Soft bottom vegetation .................................................................................. 73 7.4 Mass occurrence of macroalgae ................................................................... 74 7.5 Littoral fauna ................................................................................................... 77 7.6 Decline of Mytilus edulis ............................................................................. 77 7.7 Newcomers ....................................................................................................... 78 8 Changes in zoobenthic communities .....................................79 8.1 The Bothnian Bay ........................................................................................... 79 8.2 The Bothnian Sea ..........................................................................................